1. Field of the Invention
The present invention relates to an electro-optical device using an ionizable gaseous medium as an address element and, more specifically to an image display device adapted to drive an electro-optical material layer by making use of plasma.
2. Description of Related Art
To assure that a liquid crystal display has high resolution and high contrast, there is generally carried out a method in which active elements such as transistors, etc. are provided for every display pixels so as to drive them (which method is so called an active matrix addressing system).
In this case, however, since it is necessary to provide a large number of semiconductor elements such as thin film transistors, the yield is not good particularly when the display area is enlarged, giving rise to problems and the cost is increased.
Thus, as the means for solving this problem, Buzaku et al have proposed in the Japanese Laid Open Application No. 217396/89 publication (corresponding to U.S. Pat. No. 4,896,149 and U.S. Pat. No. 5,077,553) a method of utilizing discharge plasma in place of semiconductor elements such as MOS transistors or thin film transistors, etc. as an active element.
The configuration of an image display device for driving a liquid crystal so as to make use of discharge plasma will be briefly described below.
In this image display device, as shown in FIG. 11, a liquid crystal layer 101 serves as an electro-optic material layer and adjacent plasma chambers 102 are arranged under a thin dielectric sheet 103 comprised of glass, etc.
The plasma chambers 102 are constituted by forming a plurality of channels 105 parallel to each other in a glass substrate or base plate 104. These chambers are filled with ionizable gas. Further, pairs of electrodes 106 and 107 parallel to each other are provided in respective channels 105. The electrodes 106 and 107 function as an anode and a cathode for ionizing gas within the plasma chambers 102 so as to generate discharge plasma.
On the other hand, the liquid crystal layer 101 is held by the dielectric sheet 103 and a transparent base plate 108. On the surface at the liquid crystal layer 101 side of the transparent base plate 108, transparent electrodes 109 are formed. These transparent electrodes 109 are perpendicular to the plasma chambers 102 constituted by the channels 105. The portions where the transparent electrodes 109 and the plasma chambers 102 intersect with each other correspond to respective picture elements.
In the above-mentioned image display device, by switching and scanning in sequence the plasma chambers 102 where plasma discharge is carried out, and by applying signal voltages to the transparent electrodes 109 on the liquid crystal layer 101 side in synchronism with the switching scan operation, these signal voltages correspond to respective picture elements. The liquid crystal layer 101 is thus driven.
Accordingly, the channels 105, i.e, plasma chambers 102 respectively correspond to one scanning lines, and the discharge region is divided every scanning unit.
Meanwhile, in image display devices utilizing discharge plasma as described above, it is considered that an increased display area is more easily realized as compared to image display devices using semiconductor elements, but various problems remain in putting image display devices utilizing discharge plasma into practice.
For example, forming channels 105 for constituting respective chambers 102 at the surface portion of the glass substrate 104 serving as a transparent dielectric substrate results in considerable difficulty in manufacturing. Particularly, forming channels 105 at a high density is very difficult.
Further, in the case where there is adopted a structure such that plasma chambers 102 are respectively constituted by channels 105, liquid crystal layer 102 sections corresponding to the projected portions or the glass substrate 104, which partition respective plasma chambers 102, become ineffective and portions are not driven. In addition, at the portions where the wall surfaces of respective channels 105 are formed as a slanting surface or a curved surface, the direction or the polarized state, etc. of a transmitted light is disturbed. This is a problem so as to obtain suitable luminance control, etc.
There is the possibility that the existence of the channels 105 exerts unfavorable large influences on the contrast and the transmissivity (or transmission factor) in the case where an image display is carried out.
Further, in order to scan plasma discharge, a drive circuit having a high voltage (about 150 to 500 volts) is necessarily required. For this reason, the drive circuit unit becomes large, and the cost is also increased.
Furthermore, when an attempt is made to drive the previously described image display device in accordance with the interlaced scanning system, inconveniences such as described below take place.
In conventional PALCs, when an interlaced drive is normally carried out, respective pixels are scanned only every other field (33 mill seconds, e.g., in the case of the NTSC system). At this time, when a moving pictorial image is displayed, images before one field are left within a screen for every other line. For this reason, particularly, at the end portion of a pictorial image, disagreeable fading-out occurs, so the picture quality may be substantially degraded. In addition, because of the inversion of the polarity of the liquid crystal, flicker of two frame periods takes place.
So as to solve this problem, in the same manner as in liquid crystal devices of the TFT System, it is possible to adopt, e.g., a method of converting an interlaced scanning to a sequential scanning by an image processing, a method of inputting a signal of one line to two scanning lines which combination is changed every field, or the like.
In any case, however, there results a great load on the drive circuit such that a line memory is required, and/or the writing time every line becomes one half. This causes the cost of the device to be increased.
In order to eliminate the above noted drawbacks, it is an object of the present invention to provide an electro-optical device such as an image display device which has excellent image qualities and is easily assembled into the device.
Another object of the invention is to provide an electro-optical device in which an operable voltage drive circuit can be used, thereby permitting the cost of the device to be reduced.
A further object of the invention is to provide an electro-optical device capable of eliminating, without alteration of the drive circuit, degradation of the dynamic resolution (resolution of a moving picture) when an interlaced operation is carried out.
In accordance with the present invention, there is provided an electro-optical device comprising a first substrate, a second substrate opposed to the first substrate, an electro-optical material layer, and a discharge chamber. The first substrate has a plurality of nonoverlapping first electrodes on a major surface thereof. The second substrate has a plurality of nonoverlapping second electrodes. The first and second electrodes are disposed spaced apart in the vertical and horizontal directions, respectively. The electro-optical material layer is disposed in contact with the first electrodes of the first substrate. The discharge chamber is disposed between the electro-optical material layer and the second substrate and is filled with an ionizable gas. The discharge chamber has a plurality of scanning units. Each scanning unit comprises a discharge region of a localized volume of ionized gas so that at least two scanning units are formed in a continuous space.
The inventive device may include a dielectric material layer disposed between the electro-optical material layer and the discharge chamber.
Preferably, the discharge region of all scanning units is formed as a continuous space.
Further, the inventive device may include scanning circuits for interlaced scanning of n:1.
According to another aspect of the present invention, there is provided an electro-optical device comprising a first substrate, a second substrate opposed to the first substrate, an electro-optical material layer, a discharge chamber, a first circuit, and a second circuit. The first substrate has a plurality of first electrodes on the inner surface thereof. The second substrate has a plurality of second electrodes. The first and second electrodes are spaced apart and extend in the vertical and horizontal directions, respectively. The electro-optical material layer is disposed in contact with the first electrodes of the first substrate. The discharge chamber is disposed between the electro-optical material layer and the second substrate so that display elements are defined by overlapping areas of the first electrodes and a discharge region. The second electrodes are disposed on the second substrate so that the discharge region extends over a plurality of scanning units. The discharge chamber is filled with an ionizable gas. The first circuit generates a first electrical signal which is applied to the first electrodes. The second circuit generates a second electrical signal which is applied to the second electrodes. The ionizable gas comprises an electrical switch which changes between plasma state and de-ionized state in response to the second signal which is applied.
Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof taken in conjunction with the accompanying drawings although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which: